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Subject[PATCH tip/core/rcu 2/5] srcu: Prevent sdp->srcu_gp_seq_needed_exp counter wrap
Date
From: Ildar Ismagilov <devix84@gmail.com>

SRCU checks each srcu_data structure's grace-period number for counter
wrap four times per cycle by default. This frequency guarantees that
normal comparisons will detect potential wrap. However, the expedited
grace-period number is not checked. The consquences are not too horrible
(a failure to expedite a grace period when requested), but it would be
good to avoid such things. This commit therefore adds this check to
the expedited grace-period number.

Signed-off-by: Ildar Ismagilov <devix84@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
kernel/rcu/srcutree.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
index 01f4a8bf0e03..bb9607baad9b 100644
--- a/kernel/rcu/srcutree.c
+++ b/kernel/rcu/srcutree.c
@@ -579,6 +579,9 @@ static void srcu_gp_end(struct srcu_struct *sp)
if (ULONG_CMP_GE(gpseq,
sdp->srcu_gp_seq_needed + 100))
sdp->srcu_gp_seq_needed = gpseq;
+ if (ULONG_CMP_GE(gpseq,
+ sdp->srcu_gp_seq_needed_exp + 100))
+ sdp->srcu_gp_seq_needed_exp = gpseq;
spin_unlock_irqrestore_rcu_node(sdp, flags);
}
}
--
2.5.2
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